Editor's Note: (Michael Bociurkiw (@WorldAffairsPro) is a global affairs analyst and host of the podcast "Global Impact." He is a regular contributor to CNN Opinion and a former spokesperson for the Organization for Security and Cooperation in Europe (OSCE). The opinions expressed in this commentary are his own. Read more opinion at CNN.)
(CNN) Trying to discern Russian President Vladimir Putin's endgame is always a difficult exercise, particularly given his inclination to upset the status quo -- as he did most recently, in 2014, with the invasion of Crimea and later the Donbas region of Ukraine. But now seems to be as good a time as ever for the Kremlin to test the mettle of President Joe Biden's new administration.
Since March, Russia has been building up its troops along its western border with Ukraine. According to White House press secretary Jen Psaki, there are more Russian troops in the region now than in the run-up to Russia's annexation of Crimea in 2014. "The United States is increasingly concerned by recently escalating Russian aggressions in eastern Ukraine," she added last week.
But it's more than concerning, it's alarming. According to Ukrainian officials, the build up of Russian forces in western Russia and Crimea includes more than 50,000 Russian troops, which is about 18% of Russia's ground forces.
And yet, so far, aside from the White House and State Department's relatively guarded statements and reports that the US may be deploying two Navy warships to the Black Sea, presumably as a show of force, the Biden administration has been slow to take forceful action.
Perhaps, like so many of us in the international community, the administration is trying to figure out Putin's objective. Regardless, though, the US needs to deter any further acts of aggression or seizure of territory by making clear the consequences if Russia persists in its border activities.
It seems unlikely that Putin wants to lead a full-scale invasion of Ukraine right now, especially given the risk of significant Russian casualties during the ongoing muddy season. Instead, the build up might be an effort to place renewed pressure on Ukraine to implement the 2015 so-called Minsk framework which, in exchange for a permanent cease fire and removal of armed combatants and weaponry, would grant special status to occupied Luhansk and Donetsk in eastern Ukraine.
To a lesser extent, the Kremlin's provocative moves could be designed to show Biden that Russia still regards Ukraine as very much in its sphere of influence. With the Biden administration still mapping out its foreign policy posture, Putin may see this as the perfect time to set boundaries -- politically and militarily -- for the next four years.
Putin's latest approach -- lining troops along a contentious border -- might also be a prelude to introducing Russian "peacekeepers" in the region to maintain a permanent presence, as it has done elsewhere in the post-Soviet space.
This last scenario is one that former US ambassador to Russia Alexander Vershbow told me cannot be ruled out: "I wouldn't exclude the possibility of a unilateral deployment of Russian peacekeepers to 'protect' the poor, defenseless Russian citizens in occupied Donbas. It would enable (the Russians) to maintain the narrative that Donbas is a 'civil war' and that Ukraine, not Russia, is to blame for the dire conditions. This would avoid new bloodshed and might be greeted by some Europeans as a show of restraint rather than creeping annexation."
Though Moscow has been describing these border maneuvers as an exercise, Dmitry Kozak, a Russian official, said that his government could intervene to "defend" Russian citizens should the need arise. In fact, in the past two years, Moscow has been offering Russian passports to residents of the occupied parts of eastern Ukraine.
As tensions remain high, Ukraine has ramped up diplomatic efforts, reaching out to allies for support. Over the weekend, Ukrainian President Volodymyr Zelensky met in Istanbul with Turkish President Recep Tayyip Erdogan where he received assurances that the country would support Ukraine's territorial integrity. And in what is probably a non-starter, Zelensky repeated his plea for the West to grant his country immediate membership into NATO in an interview with CNN.
Putin, however, would never accept the extension of the western military alliance to Russia's borders. After all, it is no coincidence that, in 2014, when Ukraine was about to embark on a path to joining European Union by signing a trade pact, Moscow responded by invading Crimea and later the Donbas region.
While the diplomatic words of support expressed by allies, including the United States, are probably welcome in Kyiv, Zelensky said that, at the moment, "Ukraine needs more than words." Whether there is further goodwill for Ukraine in western capitals remains to be seen: there is plenty of disenchantment with Zelensky for badly-stalled reforms that put at risk the next tranche of a $5 billion IMF loan. In addition, the country has faced criticism of its initial response to the pandemic, and it has fallen into the unenviable position of having the worst Covid-19 infection rates in Europe.
Still, the US is unlikely to sit by and watch Zelensky struggle. Former US ambassador to Ukraine William B. Taylor said he expects further measures from the White House. "The goal is to deter any attack by indicating strong US support and the preparation of additional, harsher sanctions and other measures to further isolate Russia. The robust security assistance from the US to Ukraine continues (is also key)," he told me. And, thus far, aside from providing Javelin anti-tank missiles, the Biden administration has announced $125 million in military assistance.
But will further sanctions -- on a country that is already heavily sanctioned - have much impact on Putin? Not much, unless they include the harshest possible measures that limit the ability of the oligarchs in Putin's immediate circle to conduct financial, property and other transactions overseas. And frankly, nothing short of a multicountry coordinated move that would include the United Kingdom, a favorite investment location for Russian oligarchs, would likely influence Putin's approach to Ukraine.
At the moment, many fear that the escalation in troops will place Ukraine and Russia on a path of no return, where their disagreement can only be resolved by military means. But without an immediate, unequivocal and robust response from the US and its western allies, this is a battle Kyiv is sure to lose.